By hvhipot 
Series resonant AC withstand voltage test is to change the inductance and frequency of the experimental circuit to make it in a resonant state. This method can meet the experimental requirements of high voltage and high current. Precautions for variable frequency series resonant device in AC withstand voltage test:
(1) Before the experiment, it is necessary to understand whether the non-destructive testing items of the tested equipment are qualified. If there are defects or abnormalities, testing should be conducted after cleaning.
(2) The gap between the protective balls should be adjusted to ensure that the discharge voltage is 105% ≤ 110% of the experimental voltage There should be no significant difference in three consecutive experiments, and the reliability of the overcurrent protection device should be checked .
(3) If the pointer of the voltmeter oscillates greatly, the subject makes abnormal sounds, the milliampere indication increases sharply, and the subject continuously emits sparks such as smoke, fire, insulation, etc., the voltage should be immediately reduced. After the grounding wire is hung on the high-voltage side, the cause should be identified.
(4) The experimental site should be surrounded by fences, warning signs should be hung, and a dedicated person should be assigned to supervise;
(5) After the wiring is completed according to the experimental wiring diagram, a dedicated person should check and confirm that the wiring is correct (including the distance between the wire and the ground, safety distance, etc., and the back can be preloaded;
(6) Before pressing, check if the regulator is in the zero position and confirm if it can be pressurized after zero. Only operate after “high pressure at home”.
(7) Before the experiment, the insulation surface of the test equipment should be wiped clean, and the test equipment, test product casing, and non test winding should be reliably grounded. For multi oil equipment, the oil should be allowed to stand still for a certain period of time according to relevant regulations before conducting experiments.
(8) During the boosting process, monitoring of changes in voltage meters and other instruments should be carried out. When the additional experimental voltage is 0.5 times, the capacitance current of the tested device should be read. When the additional voltage increases, the capacitance current should be read again, and then the capacitance current should be read again. When the voltage reaches zero, the voltage should be slowly reduced to zero, and then the power should be turned off.
(9) As for the boosting speed, when the experimental voltage is lower than 30%, it can be slightly faster, and then the boosting should be uniform, with a boosting rate of about 5% of the experimental voltage/s, or an additional experimental voltage of 10-15 seconds.
(10) When there is no clear adjustment for the testing equipment, the general voltage withstand time is 1 minute, and the withstand time for insulation rods and other electrical appliances is 5 minutes. After the experiment is completed, the grounding wire should be hung in a timely manner and then connected to the relevant components. I shouldn’t have a fever.
(11) Before and after the series resonant AC withstand voltage test, the insulation resistance and absorption ratio of the tested equipment should be measured, and there should be no significant difference between the two measurement results.